In prior art, multicasting can only be controlled at interface layer, but not at data link layer or user layer. In this way, members of a multicasting group are interfaces or sub-interfaces, so a multicasting packet sender can only forward multicasting packets to interfaces without knowing anything about who will receive the multicasting packets. It is not under control whether a particular user belonging to a multicasting group has the right to send multicasting packets. Apart from that, a particular user who has sent some multicasting packets can't be precisely charged. Therefore, user level management can't be achieved at present, and it is inconvenient in practice.